AWS D3.6M and EN ISO 15618-1 are the two main standards for qualifying underwater (wet) welders. They do the same job — proving a diver-welder can produce sound welds underwater — but they come from different systems: AWS D3.6M is the American standard, EN ISO 15618-1 the European one. A key point both share: water depth is an essential variable, so a qualification is tied to the depth range it was tested at.
What each standard covers
AWS D3.6M is the American standard for underwater welding, defining weld classes (Class A, B and O) against which a welder-diver’s test pieces are assessed. EN ISO 15618-1 is the European standard for the qualification testing of welders for underwater (wet) welding. In both cases a welder-diver welds test coupons that are then examined against acceptance criteria.
Personnel and procedure are not the same
AWS D3.6M and EN ISO 15618-1 qualify the welder. Qualifying a welding procedure is a separate exercise — for wet welding that involves standards such as EN ISO 15614-9, together with the applicable construction code. A real job, for example on a pipeline, additionally needs a qualified welding procedure and often classification-society witnessing.
That is why a welder qualification on its own is never a “pipeline certification”. It is one layer of several, and honest providers describe it that way.
Why depth matters
Because depth is an essential variable in these standards, your qualification is valid for the depth range you were tested at. That makes the facility you test in important: a centre that can qualify welders at real, relevant depth — for example a deep basin with an adjustable floor — can certify to the depth band a project actually requires.
Wet versus dry (hyperbaric) welding
These standards concern wet welding, done directly in the water. Dry, or hyperbaric, welding is carried out in a sealed habitat that keeps the weld area dry. For greater depths and for critical structures such as major pipelines, dry habitat welding combined with saturation diving is typically required, because it allows higher-integrity welds under controlled conditions.
Which one do you need?
It depends on where and for whom you will work, and which code the client specifies. Some clients accept AWS D3.6M; others require EN ISO. Training under a recognised body — our underwater welding programme runs under DNV — covers the relevant route so that your qualification is accepted by the parties who matter on the job.
Frequently asked
Is AWS D3.6 or EN ISO 15618-1 better?
Neither is “better”. They are the American and European standards for the same thing — qualifying underwater welders. Which one you need depends on the client, the project and the code specified.
Does an underwater welding qualification let me weld on pipelines?
Not by itself. Welding on a pipeline additionally requires a qualified welding procedure and usually classification-society acceptance. Personnel qualification is only one layer of the requirement.
Why does welding depth matter?
Depth is an essential variable in these standards, so your qualification is valid for the depth range you tested at — which is why testing at real, relevant depth matters.
What is the difference between wet and dry underwater welding?
Wet welding is done directly in the water. Dry (hyperbaric) welding is done inside a sealed, dry habitat and is typically used for deeper or more critical work.